Generally, semiconductor devices are used in a variety of electronic applications, such as personal computers, cell phones, digital cameras, and other electronic equipment, as examples. Semiconductor devices are typically fabricated by sequentially depositing insulating or dielectric layers, conductive layers, and semiconductive layers of material over a semiconductor substrate, and patterning the various layers using lithography to form circuit components and elements thereon. In the very large scale integration (VLSI) era, metal oxide semiconductor (MOS) devices are continuously being designed smaller and smaller, and have requirements of high performance and low power consumption.
In semiconductor device manufacturing, silicides or silicide materials, which are alloys of silicon and metals, are often used. Silicides are typically formed by the reaction of a metal with silicon, and they are used in a variety of applications. For example, in transistors, silicide may be used at the source, drain and/or gate regions, or it may be used to construct gates or local interconnect lines, as examples.
Silicide materials are commonly used in advanced complimentary metal oxide semiconductor (CMOS) technology. Silicides reduce sheet resistance and contact resistance, which is particularly advantageous when a silicide is disposed over the source, drain, and gate region of a transistor, as examples, although silicides are also used in other applications.
A silicide is typically formed by depositing a metal layer such as Co or Ni over a silicon layer, and then annealing the semiconductor structure. Where the metal layer is in contact with the silicon, a silicide is formed. The un-reacted metal is then etched away. In some applications, the silicide formed is automatically aligned to the underlying polysilicon layer; thus, it is often referred to as a Self-ALigned silicide or a “salicide.”
One disadvantage of prior art methods of forming silicide materials is the phenomenon of incomplete silicidation, as shown at 128 in prior art FIG. 5, which will be described further herein. If incomplete silicidation 128 occurs in the gates of a semiconductor device 100 or integrated circuit having a plurality of transistors, for example, this is a problem, because the transistors of the device 100 have different operating characteristics. For example, transistors having gates that are fully silicided have less resistance and thinner electrical gate dielectric thickness due to no depletion of silicide gates than transistors having incompletely silicided gates, and thus, the transistors having fully silicided gates operate faster. Thus, incomplete silicidation results in decreased device performance and decreased yields.
What are needed in the art are improved methods of forming silicide materials.